Methods and devices for generating electricity from a fuel and an oxidant using a capacitor

ABSTRACT

Devices and methods are provided for generating electrical power using a capacitor. The capacitor has a catalytic working electrode, a dielectric, and a counter electrode. Power is generated by flowing a fuel (e.g., hydrogen gas) over the working electrode, charging the capacitor (e.g. by applying a voltage), flowing an oxidant (e.g., oxygen gas) over the working electrode, and connecting the electrodes to a resistive load, which allows current to flow through the load, between the electrodes. The inverse device (i.e., oxidant first, then fuel) functions similarly.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/758,764 (now U.S. Pat. No. 9,269,968), filed Feb. 4, 2013, whichclaims the benefit of U.S. Patent Application No. 61/594,839, filed Feb.3, 2012, the disclosures of which are hereby incorporated by referencein their entirety.

BACKGROUND

Fuel cells (FCs) are versatile energy conversion technology. They canconvert numerous high energy density fuels directly into electricitywithout first converting the chemical energy into thermal energy,bypassing the Carnot efficiency limitations of conventional heatengines. All conventional fuel cells consist of an anode where a fuel isoxidized and a cathode where an oxidant (typically oxygen) is reduced.The anode and cathode are separated by an ion transport membrane andconnected via an external electrical circuit, as illustrated in FIG. 1A.FIG. 1B illustrates the equivalent circuit diagram used to represent thephysical processes and test the FC with an applied voltage orsource-measure unit. The free energy of reaction drives a DC currentflow through a load in the external circuit while ions (typically H⁺,OH⁻, CO₃ ²⁻, or O²⁻) flow through the membrane. In addition to theirpotential for high efficiency, fuel cells may be operated with cleanfuels such as hydrogen (yielding water as the only exhaust) orsustainable biofuels that are carbon neutral (produce no net CO₂). Fuelcells come in many different varieties with a wide range of potentialapplications. High temperature fuel cells (solid oxide fuel cells,SOFCs) have typically been considered for stationary power, and lowtemperature fuel cells (proton exchange membrane fuel cells, or PEMFCs)have typically been considered for transportation or portable power. FCsyield high power density (especially when compared to technologies likesolar energy). But still, market penetration for both PEMFCs and SOFCsis low due to high cost and reliability issues. The typical powerdensity for a commercial PEMFC is around 600 mW/cm², while that for anSOFC is around 300 mW/cm². In 2009 the U.S. Department of Energy setfuel cell cost and lifetime goals to be $750/kW with 40,000 hours ofoperation for stationary power and $30/kW with 5,000 hours of operationfor the transportation sector.

SOFC technology appears to be mature enough and poised for commercialsuccess, particularly for stationary power applications where thevaluable heat may be utilized and the net efficiency increased. Theincreased market penetration that now seems possible for SOFCs isactually a positive development for other fuel cells technologies aswell. Some technologies have intrinsic advantages for applications suchas transportation or portable power, but further development is hinderedby the perception that FCs are problematic. The quick response time andlow operating temperature are key for automotive and portable powerapplications. For these applications particular focus has been paid toPEMFCs. However there are many barriers to PEMFC development andcommercialization. Scientific challenges still exist to improve theoxygen reduction reaction (ORR) catalyst, prevent poisoning of thehydrogen oxidation reaction (HOR) catalyst, and develop highertemperature proton conducting membranes. In addition there are morepractical issues which need to be addressed like active water managementto maintain membrane wetness without flooding, improving devicereliability, and lowering system cost. Also, it could be viewed eitheras a liability or a great benefit, but the most advanced PEMFCs usehydrogen as the fuel. Below, we review some of the issues withconventional PEMFCs and review some novel fuel cell design conceptswhich seek to bypass the limitations of conventional devices, such assingle-chamber and membraneless designs.

Conventional Proton-Exchange Membrane Fuel Cells (PEMFCs)

The oxidation of hydrogen to yield water is given by the followingfamiliar reaction:

$\left. {H_{2_{(g)}} + {\frac{1}{2}O_{2_{(g)}}}}\rightarrow{H_{2}O_{(l)}} \right.$${\Delta \; G^{{^\circ}}} = {237\frac{kJ}{mol}}$Δ E^(^(∘)) = 1.23  V${\Delta \; H_{rxn}^{{^\circ}}} = {286\frac{kJ}{mol}}$

This simple and clean reaction has tremendous appeal for using hydrogenas an energy carrier, especially when combined with renewable (solar orwind generated) hydrogen. The fly in the ointment that tempers one'senthusiasm for the fuel though is the difficulty with storing anddistributing hydrogen. In addition, the low temperature fuel celltechnology that converts it to electricity (the PEMFC) has severalproblems that have prevented its cost effectiveness and thus itswidespread adoption. A summary of some of the most significant problemsare presented below.

Catalysts for the Oxygen Reduction Reaction: High ActivationOverpotential

The oxidation reduction reaction (ORR) is puzzling in that it is one ofthe oldest known electrochemical reactions, and yet it remains one ofthe most poorly understood. Numerous mechanisms have been proposed forthe ORR on platinum, and the most widely accepted mechanism is theassociative adsorption mechanism:

O₂→O₂ _(ads)   (rxn1)

O₂ _(ads) +H_(ads) ⁺ +e ⁻→HO₂ _(ads)   (rxn2)

HO₂ _(ads) +H_(ads) ⁺ +e ⁻→H₂O+O_(ads)  (rxn3)

O_(ads)+H_(ads) ⁺ +e ⁻→HO_(ads)  (rxn4)

HO_(ads)+H_(ads) ⁺ +e ⁻→H₂O  (rxn5)

The rate determining step is thought to be reaction rxn2 above, but thedebate over mechanism and rate limiting step remains open. Increasingits reaction rate can dramatically improve fuel cell performance.Research on the ORR has focused mainly on the development of newcatalysts. While the overall rate can also be increased by simplyincreasing the temperature beyond the 80° C. where PEMICs are typicallyoperated, this causes other issues, particularly with the ion transportmembrane as discussed below.

Catalysts for the Hydrogen Oxidation Reaction: Poisoning

Carbon monoxide, sulfur, and other species can poison the HOR catalyst,typically platinum. This phenomenon is well known and has been recentlyreviewed. Since CO is a by-product of the reforming process throughwhich most hydrogen is produced (FIG. 2), it is a serious impediment tothe development of PEMFC technology. CO poisons a platinum catalyst bystrongly chemisorbing to the surface and blocking the active reactionsite. The easiest way to overcome the problem of CO poisoning is toincrease the operating temperature. The tolerance of CO is directlyrelated to temperature. Increasing the temperature to as little as 130°C. dramatically improves PEMFC performance in the presence of CO.However, as the temperature is increased, the PEM dries out and theseries resistance increases leading to lower efficiency. Theconventional approach is to develop an alternative to the Nafion polymerused in current technology or develop catalysts that are more tolerantto the presence of CO. However, other interesting ideas have beenproposed. For instance, it has been proposed to inject oxygen orhydrogen peroxide into the fuel stream to oxidize CO before it reachesthe catalyst. However, the poisoning issue is pernicious and unresolved.

Both ORR and HOR Catalysts: Degradation

Another problem with conventional PEMFC catalysts is degradation.Platinum particle dissolution and agglomeration and carbon supportreaction are the main mechanisms of degradation, and both arefacilitated by the presence of water. If the carbon support and liquidwater were eliminated, many of the degradation concerns would bealleviated.

Membrane Humidification: Kinetics better at Higher Temperature, but theMembrane Dries Out

PEMFC technology has as one of its primary advantages that it operatesat a low temperature. However by increasing the temperature, fuel cellperformance can be greatly improved. This is primarily due to theimprovement in exchange current density, but performance improvementsare also observed in efficiency due to better heat and water management.However the membrane in typical PEMFCs needs to be humidified for facileion transport. This is because the proton conductivity of Nafion, thestandard PEMFC membrane material, drops as the membrane dries causing anincrease in ohmic losses and ultimately leads to device failure. To getaround this problem it is necessary to have an external humidifier torun PEMFCs at higher temperatures. Also, because they have a hydratedmembrane, PEMFCs can also suffer catastrophic failure in sub-freezingenvironmental conditions. Getting around these limits requires thedevelopment of new membrane materials, which is a highly active field ofstudy. However at present no alternative membrane technologies have bothhigh performance and robust operation at high temperature. This issuewith proton exchange membranes has prompted the development of severalunconventional fuel cell designs.

Unconventional Fuel Cell Designs

In order to circumvent many of the issues discussed above, entirely newdevice architectures have been proposed. These include so called“single-chamber” designs and “membraneless” designs. A summary of a fewof these devices is provided below.

Single-chamber fuel cell concepts (FIGS. 3A and 3B) were considered asearly as the late 1950s. But in 1990, a single-chamber design generatedboth interest and controversy. The device functions similar to aconventional PEMFC with the major exception that the hydrogen and oxygenare mixed and fed to the same side of the device. The mechanism ofoperation has been debated, but the devices were able to achieve about 1volt and power densities of 1 to 5 mW/cm². The design has the advantagethat it does not need seals and could be fabricated in a simple manner.However, since hydrogen is also present at the outer electrode, there isa substantial chemical (not electrochemical) reaction rate betweenhydrogen and oxygen, which represents a significant loss in efficiency.Interestingly, it was noted that high humidification and low pressuresreduced this undesirable side reaction. Others later developed a twosided design with selective catalysts (FIG. 3B) that operates moresimilar to an SOFC. This latter device also generated significantinterest and spawned several research efforts.

Another unconventional design uses mass transport limitations to keepfuel away from the cathode and the oxidant away from the anode. These“membraneless” designs do not have a membrane, but they still requirethe DC transport of an ion—typically diffusion across a laminar flowfield in a microfluidic channel. The fuel and oxidant streams are mergedat a y-junction (FIG. 4) at low Reynolds number (Re<10). As the fluidflows down the channel, the fuel and oxidant species begin to diffuseacross the channel creating a diffusion zone which acts quite similar toa membrane in a conventional fuel cell. One advantage of this design isits simplicity and compact size, but they yield very low powerdensities, have very poor fuel efficiency, and require continuous liquidflow (and perhaps recycling).

In short, both of these unconventional fuel cell designs have someunique traits, but neither addresses the key issues with low temperaturefuel cell technology without creating more serious problems (such as lowfaradic efficiency). The high cost of platinum and Nafion, the lowtemperature HOR poisoning, ORR and HOR catalyst degradation, thepresence of liquid water, and the difficulty of actively managing waterall combine to provide significant technical and reliability barriersthat inhibit PEMFC technology.

A solution that avoids these issues would be a breakthrough that wouldsignificantly alter and enhance the prospects for low-temperature fuelcell technology.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This summary is not intended to identify key features ofthe claimed subject matter, nor is it intended to be used as an aid indetermining the scope of the claimed subject matter.

In one aspect, a method of generating electricity from a fuel and anoxidant is provided. In one embodiment, the method includes the stepsof:

(a) immobilizing the fuel on a working electrode of the capacitor by:

-   -   exposing the working electrode to the fuel, wherein the working        electrode comprises a catalyst for an electrochemical reaction        between the fuel and the oxidant; and    -   charging the capacitor by biasing the working electrode such        that it becomes positively charged and biasing a counter        electrode of the capacitor such that it becomes negatively        charged, wherein a dielectric of the capacitor separates the        counter electrode from the working electrode, and wherein        charging the capacitor is performed either before or after        exposing the working electrode to the fuel;

(b) exposing the working electrode to the oxidant after the fuel hasbeen immobilized on the working electrode; and

(c) generating electrical power by connecting an electrical load betweenthe working electrode and the counter electrode.

In another aspect, another method of generating electricity from a fueland an oxidant is provided. In one embodiment, the method includes thesteps of:

(a) immobilizing the oxidant on a working electrode of the capacitor by:

-   -   exposing the working electrode to the oxidant, wherein the        working electrode comprises a catalyst for an electrochemical        reaction between the fuel and the oxidant; and    -   charging the capacitor by biasing the working electrode such        that it becomes negatively charged and biasing a counter        electrode of the capacitor such that it becomes positively        charged, wherein a dielectric of the capacitor separates the        counter electrode from the working electrode, and wherein        charging the capacitor is performed either before or after        exposing the working electrode to the fuel;

(b) exposing the working electrode to the fuel after the oxidant hasbeen immobilized on the working electrode; and

(c) generating electrical power by connecting an electrical load betweenthe working electrode and the counter electrode.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same become betterunderstood by reference to the following detailed description, whentaken in conjunction with the accompanying drawings, wherein:

FIG. 1A is a schematic of a PEMFC and FIG. 1B is its equivalent circuitdiagram used to represent the physical processes and test the FC with anapplied voltage or source-measure unit. The capacitors here are due tothe non-faradic electrochemical double layer charging while R_(a) andR_(c) are faradic charge transfer resistances due to the ORR and HOR.R_(m) is then the series resistance due to proton transport through themembrane.

FIG. 2. Fuel reforming for various FC types.

FIGS. 3A and 3B. Single-chamber mixed-gas fuel cell designs. FIG. 3A:Single-side gas exposure with non-selective electrodes. FIG. 3B:Two-sided gas exposure with selective electrodes.

FIG. 4. Design of a membraneless laminar flow fuel cell.

FIG. 5A. Principle steps of operation for a metal-insulator-metal (MIM)fuel cell: (1) Adsorption—Diluted H₂ in N₂ flows into the reactionchamber, adsorbs, and dissociates while the device is held at opencircuit conditions. (2) HOR/Charging—The circuit is completed and avoltage is applied across the metal-insulator-metal (MIM) device from anexternal power supply. The adsorbed hydrogen atoms are oxidized. Theenergy paid by the power supply is stored in the electric field at thesurface surrounding the adsorbed H⁺ and in the polarized dielectric.C_(MIM) is the capacitance of the device and R_(HOR) is the chargetransfer resistance. (3) Change Vapor Phase—The circuit is opened andthe hydrogen gas is purged from the chamber with an inert while avoltage exists across the device. Air or oxygen is then flowed into thechamber. The voltage across the device will then rise by V_(ORR) asoxygen interacts with the H_(ads) ⁺, adding an additional driving forcefor electrons flow back to the working electrode. (4)ORR/Discharging—The electrical circuit is then completed providing apath for the electrons to flow through the load. O₂ and 2H_(ads) ⁺combine with 2e⁻. For an ideal system (no ohmic loss, no leakage throughthe dielectric, and no parasitic reactions) the energy output of thedevice would be equal to the energy of the reaction of surface protonsand oxygen to form water, minus the energy to strip the electrons.

FIG. 5B illustrates a method and device similar to FIG. 5A but withoutan external voltage applied to bias the device. The device is insteadcharged by exposing the working electrode to the fuel to the extent thatthe device is polarized.

FIG. 6. The theoretical response versus time for the 4 step cycle shownin FIG. 5A. The voltage, current, and power vs. time are sketched andare labeled to indicate the step to which they correspond.

FIGS. 7A-7C. Schematic of rotating disk design with two MIM stacks onthe disk. A top-view of the cylindrical device is shown (FIG. 7C) whiletwo cross sectional views are shown (FIGS. 7A AND 7B) for two differenttimes. Note that the disk has rotated 180° between the top and bottomfigure. The current that flows is AC and has the waveform shown in FIG.8 below. Also, a porous layer above the MIM may be used to preventdamage to the MIM from the seal on the separator.

FIG. 8. Expected AC waveform from the device shown in FIGS. 7A-7C can beconditioned to a standard 60 Hz sine wave with conversion efficiencyC_(e), where 0≦C_(e)<1 and V_(o) is the maximum amplitude of thepre-processed signal.

FIG. 9. Experimental setup for gas flow method.

FIG. 10. Detail of a metal-insulator-metal device and sample holder.

FIG. 11 illustrates a representative method for providing fuel andoxidant to generate electrical power using a capacitor, in accordancewith the embodiments provided herein.

FIG. 12 illustrates an exemplary system for generating power using“packed bed” configurations of capacitors connected to fuel and oxidantdelivery systems.

FIGS. 13A and 13B illustrate an exemplary rotating device system thatincludes two rotated working electrodes and stationary gas phases. FIG.13A is a perspective view and FIG. 13B is a top plan view.

FIG. 14A illustrates a three-chamber rotating disk device wherein a fuelchamber, an oxidant chamber, and an exhaust chamber are all disposedseparately above the rotating disk. FIG. 14B is a modified version ofthe device of FIG. 14A, wherein the fuel chamber is larger than theoxidant and exhaust chambers.

FIG. 15A illustrates a “conveyor belt” style device whereby a pluralityof capacitors are mounted on a belt that mechanically moves thecapacitors between a fuel region and an oxidant region (hydrogen andair, respectively). FIG. 15B illustrates an alternative “two-sided” MIMdevice that could be used with the conveyor belt system of FIG. 15A.

FIGS. 16A and 16B illustrate double-sided disk devices, wherein amechanical support is used to support capacitors mounted to both a topand a bottom side of the support.

FIGS. 17A and 17B illustrate an exemplary device configuration having anenhanced-area working electrode. An overhead view is illustrated in FIG.17A, and a cross-sectional view is illustrated FIG. 17B.

FIGS. 18A and 18B illustrate schemes for a rotating disk device wherebymultiple working electrodes are used (FIG. 18A) and multiple gas chamberare used (FIG. 18B) to increase the frequency of the power generated bythe devices.

FIGS. 19A and 19B illustrate a cylindrical electrode design whereincapacitors are mounted on a cylinder spinning between a fuel region andan oxidant region. FIG. 19B is a detail of the MIM-mounted cylinder ofFIG. 19A.

FIG. 20 a “triangular shaft” design is provided, whereby a triangularshaft has capacitors mounted on all three surfaces of the triangularshaft.

FIG. 21. A Wankel-type system is illustrated whereby a non-symmetric,three-surface shaft is used to control intake, compression, and exhaustin a rotating shaft system.

DETAILED DESCRIPTION

Disclosed herein is a novel membraneless fuel cell (also referred to asa “capacitor” herein) design that can be used to directly generatealternating current (AC) power or pulsed DC power. The capacitorrequires no ion transport, no liquid water, no carbon, and has norestrictions on operating temperature.

In one aspect, a method of generating electricity from a fuel and anoxidant is provided. In one embodiment, the method includes the stepsof:

(a) immobilizing the fuel on a working electrode of the capacitor by:

-   -   exposing the working electrode to the fuel, wherein the working        electrode comprises a catalyst for an electrochemical reaction        between the fuel and the oxidant; and    -   charging the capacitor by biasing the working electrode such        that it becomes positively charged and biasing a counter        electrode of the capacitor such that it becomes negatively        charged, wherein a dielectric of the capacitor separates the        counter electrode from the working electrode, and wherein        charging the capacitor is performed either before or after        exposing the working electrode to the fuel;

(b) exposing the working electrode to the oxidant after the fuel hasbeen immobilized on the working electrode; and

(c) generating electrical power by connecting an electrical load betweenthe working electrode and the counter electrode.

A traditional fuel cell has two electrodes: a dedicated cathode and adedicated anode. It produces DC electricity when electrons move throughan external circuit while a steady flow of protons move through theinternal membrane that separates the two electrodes. Contrary to thisscheme, in the disclosed embodiments, the same physical electrodesurface alternates between being the site of the cathodic reaction andthe anodic reaction, and thus the proton stays on the electrode whilethe electrode is exposed to different gas phase environments. The gasmay be changed by either flowing in a different gas, translating theelectrode into a different environment, or rotating the electrode into adifferent environment. With the addition of a dielectric layer under thecatalyst (to help the electrode support more surface charge density) anda switching circuit, the device produces pulsed DC or AC current withnet electrical power output.

The disclosed device consists of a planar metal-insulator-metal (MIM)(“capacitor”) architecture. The top metal electrode (the workingelectrode, WE) is chosen to be catalytically active for both the HOR andthe ORR, and the bottom metal electrode (the counter electrode, CE) ischosen only for its conductivity, adhesion, and convenience. For anexemplary device, platinum is used for the WE and aluminum or gold forthe CE. The choice of the dielectric layer is important and will bediscussed below in greater detail. The device operates in a cyclicfashion with the four steps shown in FIG. 5A. After the ORR in the finalstep, the cycle could be repeated to create pulsed DC power, or twodevices can be combined to yield AC power.

Note that for the exemplary device illustrated in FIG. 5A, the HORrequires power to be input into the device. The goal is for theelectrical power output during the ORR to be more than the power inputduring the HOR. The expected voltage, current, and power versus time forone complete cycle shown in FIG. 5A is plotted in FIG. 6. The exemplarydevice illustrated in FIG. 5B requires no external power to be input(i.e., no bias) into the device. Instead, the device is charged throughthe interaction of the fuel with the working electrode, whichsufficiently polarizes the device (e.g., through adjusting the Fermilevel of the WE) so as to provide a charged state that facilitates theremaining steps of the process.

During Step 1, H₂ (fuel) flows into reaction chamber and adsorbs on thePt surface where it dissociates spontaneously. The quantity adsorbedwill be determined by the platinum loading, dispersion, partial pressureof H₂, the presence of any competitive adsorbates, and the condition ofthe catalyst surface. During this step, no significant current flows andthere is virtually no change in the voltage across the device.

During Step 2, a voltage is applied, the HOR proceeds creating H_(ads)⁺, electrons flow out of the WE (current flows into the WE), and thedevice charges. The current dies off exponentially since it is simplythe charging of a simple RC series circuit, and the voltage plateaus tothe value of the applied voltage. The power input is just the currenttimes the voltage.

It will be appreciated that the ordering of Steps 1 and 2 can bereversed, in that the capacitor can be charged before exposing it to thefuel. The end result of Steps 1 and 2 are the same, however, regardlessof the order, in that immobilized (e.g., adsorbed) fuel is provided (oroxidant, in an oxidant-first process).

During Step 3, hydrogen is flushed from the chamber with an inert (toavoid any possibility of explosive mixtures of H₂ and O₂), and oxygen(oxidant) is flowed in. Since the electrical circuit is still open,current does not flow, H_(ads) ⁺ stays on the surface, but the voltagedoes rise due to the presence of oxygen. Ideally, the change in voltageshould be 1.23 V.

During Step 4 (the power output step), the electrical circuit is closedand the ORR begins to consume H_(ads) ⁺. The WE discharges, pullingelectrons through the load. By virtue of the extra driving forcegenerated by the oxygen presence (the free energy of the ORR), there isthe potential to extract more power during the discharge step than thecharging step. The conditions most favorable to recover this work are tolet the ORR proceed slowly. Specifically, one should not be in akinetically limited discharge regime. This can be achieved by making theload resistance large, which effectively makes the discharge stepNernstian.

Increasing the magnitude of the load resistance in this circuit isanalogous to increasing the mass transport resistance inchronoamperometry or cyclic voltammetry. The slow kinetics of thereaction can be given the time it needs by keeping the reactiontransport limited. Thus, at all times, the WE is in equilibrium with theconcentration on the electrode. As a result, the shape of the voltagedecay is determined by the Nernst equation, which decreaseslogarithmically with decreasing surface concentration. Referring to FIG.6, theoretically the area above the I(t) during step 2 should equal thearea under the I(t) during step 4 due to charge conservation. Also, dueto the increased voltage, the power output in step 4 is greater than thepower input in step 2 (see FIG. 6). The simple MIM device consists oflittle more than the structure shown in the middle column of FIG. 5Ainside an enclosure to control the gas phase environment, temperature,etc. This is described in more detail below.

In one embodiment, the step of charging the capacitor results fromexposing the working electrode to the fuel without additional appliedbias. As noted above, FIG. 5B requires no external power to be input(i.e., no bias) into the device. It will be appreciated that while manyof the exemplary devices provided herein are described in the context ofa device charged by an external power source (e.g., FIG. 5A), any suchdevice can also be implemented without external power as long as theintroduction of fuel (or oxidant) to the working electrode is sufficientto charge the device. That is, charging without external power can beaccomplished by selecting a fuel, WE, catalyst, CE, and dielectric suchthat the capacitor is polarized and charged upon exposure to the fuel(or oxidant in the case of an oxidant-first process). In the context ofFIG. 5B, this means that Steps 1 and 2 are essentially a single stepbecause exposing the WE to the fuel (or oxidant, in an oxidant-firstprocess) also charges the capacitor.

In one embodiment, the step of charging the capacitor comprises applyinga voltage between the working electrode and the counter electrode, asillustrated in FIG. 5A.

In one embodiment, the step of charging the capacitor by applying avoltage is performed prior to the step of exposing the working electrodeto the fuel.

In one embodiment, the method further comprises a step of disconnectingthe applied voltage between the working electrode and the counterelectrode, prior to the step of exposing the working electrode to theoxidant.

In one embodiment, exposing the working electrode to the fuel providesadsorbed fuel on the working electrode.

In one embodiment, charging the capacitor provides oxidized or partiallyoxidized fuel on the working electrode and stored electrons in thecounter electrode.

In one embodiment, the step of generating electrical power by connectingan electrical load between the working electrode and the counterelectrode generates electrical power by providing the stored electronsin the counter electrode to the adsorbed fuel on the working electrode,thereby allowing the adsorbed fuel on the working electrode to reactwith the oxidant to produce an oxidant-fuel product.

The “fuel first” device is disclosed in the above aspect andembodiments. However, it will be appreciated that devices wherein theoxidant is first applied to the working electrode, with subsequentlyapplied fuel to generate electricity.

Accordingly, in one aspect, an “oxidant first” method is provided. Thecapacitor device used can be the same or different from the “fuel first”device, however the structure is generally the same:

-   -   a working electrode, wherein the working electrode comprises a        catalyst for the electrochemical reaction between the oxidant        and the fuel;    -   a counter electrode; and    -   a dielectric that separates the working electrode and the        counter electrode.

In one embodiment, the “oxidant first” method includes the steps of:

(a) immobilizing the oxidant on a working electrode of the capacitor by:

-   -   exposing the working electrode to the oxidant, wherein the        working electrode comprises a catalyst for an electrochemical        reaction between the fuel and the oxidant; and    -   charging the capacitor by biasing the working electrode such        that it becomes negatively charged and biasing a counter        electrode of the capacitor such that it becomes positively        charged, wherein a dielectric of the capacitor separates the        counter electrode from the working electrode, and wherein        charging the capacitor is performed either before or after        exposing the working electrode to the fuel;

(b) exposing the working electrode to the fuel after the oxidant hasbeen immobilized on the working electrode; and

(c) generating electrical power by connecting an electrical load betweenthe working electrode and the counter electrode.

It will be appreciated that while fuel-first devices are primarilydescribed herein, any such device can be implemented in an oxidant-firstconfiguration by adjusting the method to have a working electrodecapable of adsorbing the oxidant and to have the oxidant applied to thedevice before the fuel.

In one embodiment, the step of charging the capacitor results fromexposing the working electrode to the oxidant without additional appliedbias.

In one embodiment, the step of charging the capacitor comprises applyinga voltage between the working electrode and the counter electrode.

In one embodiment, the step of charging the capacitor by applying avoltage is performed prior to the step of exposing the working electrodeto the oxidant.

In one embodiment, the method further comprises a step of disconnectingthe applied voltage between the working electrode and the counterelectrode, prior to the step of exposing the working electrode to thefuel.

In one embodiment, exposing the working electrode to the oxidantprovides adsorbed oxidant on the working electrode.

In one embodiment, charging the capacitor provides reduced or partiallyreduced oxidant on the working electrode and stored positive charge inthe counter electrode. In one embodiment, the step of generatingelectrical power by connecting an electrical load between the workingelectrode and the counter electrode generates electrical power byproviding the stored positive charge in the counter electrode to theadsorbed oxidant on the working electrode, thereby allowing the adsorbedoxidant on the working electrode to react with the fuel to produce anoxidant-fuel product.

Composition of the Fuel, Oxidant, and Capacitor

The general composition of the fuel, oxidant, and capacitor will now bedescribed.

The fuel is a source of electrons. A typical fuel is hydrogen, althoughthe method is not limited to the use of hydrogen fuel. However, severalexemplary embodiments are described and/or illustrated using hydrogen asthe fuel. It will be appreciated that any reference to hydrogen isexemplary and that any fuel could be substituted for hydrogen in suchembodiments.

In one embodiment, the fuel is a neutral or ionic form of one or more ofthe following: hydrogen (H₂ or H); CO; N₂; NO; NO₂; sulfur; SO₂; syngas;hydrogen sulfide; hydrogen peroxide; lower alkanes (e.g., methane,ethane, etc.); all alkanes (including linear, branched, and cyclicspecies such as n-dodecane, isopentane, and cyclohexane, etc.); allalkenes (ethylene, propylene, etc.); all alkynes; all arenes (benzene,toluene, p-xylene, etc.); lower alkane alcohols (e.g., methanol,n-propanol, n-butanol, isobutanol, etc.); partially oxidized,hydroxylated, or sulfonated alkanes, alkenes, alkynes, and arenes;traditional motor fuels (e.g., gasoline, kerosene, diesel, JP12, andcrude oil); biofuels (e.g., ethanol, cellulose, sugars, bio-oils fromalgae, etc.); lower amines (e.g., ammonia, hydrazine, methyl amine,etc.); boranes (e.g., borane, ammonia borane, diborane, etc.); acids(e.g., HCl, etc.); halogens (Cl2, Br2, etc.); solvated metal cations(e.g., V+2, Mn+2, Cr+3, and all other oxidation states); solvated metalsand metal containing compounds (oxides, sulfides, hydroxides, hydrides,carbonyls, etc.); particulate metals and metal containing compounds(oxides, sulfides, hydroxides, hydrides, carbonyls, etc.); nanoparticlesof any of the preceding; any chemical species that can beelectrochemically oxidized; mixtures of any of the preceding; dilutionsof the preceding with a solvent (e.g. water, dimethyl sulfoxide,acetonitrile, hexane, toluene, etc. to form fuels such as methanol indimethyl sulfoxide, etc.) or gas (e.g., nitrogen, argon, carbon dioxide,etc. to form fuels such as hydrogen in nitrogen, etc.); and humidifiedversions of any of the preceding (e.g., hydrogen gas diluted withnitrogen gas that is humidified with water vapor).

The oxidant is a receptor of electrons. A typical oxidant is oxygen(e.g., as a component of air), although the method is not limited to theuse of oxygen as an oxidant. However, several exemplary embodiments aredescribed and/or illustrated using oxygen as an oxidant. It will beappreciated that any reference to oxygen or air is exemplary and thatany oxidant could be substituted for oxygen or air in such embodiments.

In one embodiment, the oxidant is air or a neutral or ionic form of oneor more of the following: oxygen, ozone, hydrogen peroxides, allperoxides, fluorine, chlorine, bromine, iodine, inorganic acids (e.g.,nitric, sulfuric, hydrochloric, formic), organic acids (e.g., aceticacid, citric acid, etc.), hypochlorite, chlorate, water, solvated metalcations (e.g., V+5, Mn+7, Cr+6, and all other oxidation states),solvated metals and metal containing compounds (oxides, sulfides,hydroxides, hydrides, carbonyls, etc.), particulate metals and metalcontaining compounds (oxides, sulfides, hydroxides, hydrides, carbonyls,etc.), nanoparticles of any of the preceding, any chemical species thatcan be reduced, mixtures of any of the preceding, dilutions of thepreceding with a solvent (e.g. water, dimethyl sulfoxide, acetonitrile,hexane, toluene, etc. to form an oxidant such as hydrogen peroxide inwater, etc.) or gas (e.g., nitrogen, argon, carbon dioxide, etc. to forman oxidant such as chlorine in nitrogen, etc.), and humidified versionsof any of the preceding (e.g., oxygen gas diluted with argon gas that ishumidified with water vapor).

In one embodiment, the working electrode catalyst is selected from thegroup consisting of Pt, Pd, all noble metals, Ni, Co, Cu, all transitionmetals, alloys of the preceding, oxides (e.g., ceria, zirconia, yittria,YSZ, LSY, samaria, nickel oxide, etc.), supported catalysts (e.g.,metals dispersed on oxides, carbon or other metals such as Pt), andcombinations thereof.

In one embodiment, the counter electrode is selected from the groupconsisting of Al, Cu, Ni, Zn, steel, stainless steel, Pt, any metal,transparent conductors (e.g., ITO, FTO, etc.), conducting polymers(e.g., TCNQ, PEDOT:PSS, etc.), carbon materials (e.g., nanotubes,graphene, graphite, and conducting carbon), doped silicon (n-Si orp-Si), heavily doped silicon (n+-Si or p+-Si), any doped or heavilydoped semiconductor, nanowires or nanoparticles of the preceding, andcombinations thereof.

In one embodiment, the dielectric layer is selected from the groupconsisting of SiO₂, HfO2, ZrO₂, ZrSiO4, SiHfO2, Al₂O₃, all oxides, ZnS,CdS, all sulfides, ZnSe, CdSe, all selenides, SiN, BN, GaN, allnitrides, diamond, silicon, SiC, all carbides, SrTiO3, barium strontiumtitanate, all ferroelectrics, polyimide, mylar, all polymers, all blockcopolymers, all ionic liquids, an ion-gel, air, vacuum, water, anydielectric material, and combinations or layer of any of the preceding.

In one embodiment, the capacitor further comprises a porous layercovering the working electrode, wherein the porous layer allowsdiffusion, transport or vertical passage of the fuel or the oxidant tothe working electrode from a space above the working electrode, butreduces diffusion, transport or horizontal passage (parallel to theporous layer surface) of the fuel or oxidant.

In one embodiment, the method further comprises an enhanced dielectriccoating on the working electrode, the enhanced-dielectric coating havinga dielectric constant higher than that of the working electrode. In oneembodiment, the enhanced-dielectric layer is selected from the groupconsisting of a porous high dielectric constant film (e.g., HfO2, ZrO₂,etc.), a high dielectric constant liquid (e.g., water, DMSO, etc.), or acombination thereof (e.g., coat with a high dielectric constant porousfilm and fill the pores with a high dielectric constant liquid).

Characteristics of the Electrical Load

In one embodiment, the electrical load is large such that the dynamicsof the discharge do not exceed the dynamics of the working electrodereaction (e.g., the ORR for the case where hydrogen is initiallyadsorbed to the working electrode surface).

In one embodiment, the electrical load is entirely resistive.

In one embodiment, the electrical load has capacitive or inductivecomponents.

In one embodiment, the magnitude of the electrical load is increased orreduced to increase the efficiency of the electricity generation.

Process Controls

In one embodiment, the method further comprises controlling the pressureabove the working electrode to control coverage or adsorption of thefuel and/or the oxidant. Any given system (i.e., working electrode,fuel, and oxidant), will have optimal pressures for the fuel andoxidant. These pressures result from a need to quickly cover the surfaceof the working electrode with the fuel and oxidant, although too muchsurface coverage may result in efficiency losses.

In one embodiment, the method further comprises controlling thecomposition of the fuel or oxidant phase to control coverage oradsorption. The partial pressure of the fuel is set such that only thequantity necessary for the reaction is adsorbed onto the workingelectrode. Any additional adsorption will be consumed by parasiticprocesses (e.g., leakage currents), and would represent inefficiency inthe system.

In one embodiment, the method further comprises controlling thetemperature of the working electrode to control coverage, adsorption,absorption, or kinetics at the working electrode.

Exemplary Scheme for Continuous Operation and AC Power

The amount of power generated by a single capacitor can be enhanced byincreasing the surface area of the working electrode and/or cycling thedevice frequently (e.g., many times per second). Schemes for cycling aredescribed below.

Referring to FIGS. 7A-7C, one embodiment is provided where two separateMIM devices labeled 1 and 2 are mounted on a plate. The gas phases abovethem are kept separate by a separator and a seal. At some initial time,MIM 2 is exposed to oxygen in chamber 2 and is beginning its ORR(discharging, as shown in FIGS. 5A and 6, step 4) while connected to oneside of the load. At the same moment MIM 1 is exposed to hydrogen inchamber 1 and beginning its HOR (charging, as shown in FIGS. 5A and 6,step 2) while connected to the other side of the load. MIM 2 will pullelectrons from the working electrode of MIM 1 through the load. Afterthe decay of the voltage, the plate is rotated such that MIM 2 is inchamber 1 and MIM 1 is in chamber 2. The reaction may be run again, butthis time it will pull current through in the opposite direction. Thegasses stay stationary, but the plate rotates, creating AC power at thefrequency of rotation. This AC signal would not be in the sinusoidalform of conventional AC power, but it could be conditioned into a sinewave quite easily (FIG. 8). Brush contacts allow the rotation of theplate while still contacting the plate electrically.

In one embodiment, the capacitor is the electrical load for a secondcapacitor. For example, the voltage applied to one capacitor deviceduring step (b) of either the fuel-first or oxidant-first methods issupplied by step (d) of a similar method operating on a separatecapacitor device.

Pulsed Gas Systems

In certain embodiments, pulsed gas systems are provided whereby thecapacitor device is essentially stationary and the fuel and oxidant arepassed above the working electrode in phases so as to perform the stepsof the power-generation method.

The general experimental apparatus and MIM device are shownschematically in FIGS. 9 and 10. A small chamber is fabricated to holdthe MIM device. It has ports for electrical feed-throughs (push-pincontacts), ports for pressure, temperature, and hydrogen concentrationmeasurements. The later is important to ensure there is never anexplosive mixture in the cell. The chamber has a small volume and isrelatively flat so as to reduce the time it takes to flush out one ofthe gasses.

An exemplary MIM device is illustrated in FIG. 10 and is constructedlayer-by-layer. First, a layer of aluminum (200 nm) is deposited onto acleaned substrate by thermal evaporation to form the counter electrode.A dielectric, such as Kapton, silica, or a high-k dielectric material isformed on the aluminum layer. The dielectrics tested can be prepared andapplied using a sol gel spin coating method or other method known tothose of skill in the art. Lastly, the platinum working electrode isdeposited by evaporation or coating the dielectric layer with Ptnanoparticles or nanowires to provide more interfacial area between thePt and the dielectric.

FIG. 11 illustrates a representative method for providing fuel andoxidant to generate electrical power using a capacitor, in accordancewith the embodiments provided herein. Referring to FIG. 11, a fuel (H₂)and an oxidant (O₂) are passed above the working electrode of acapacitor. In the illustrated embodiment, an inert gas (N₂) is providedintermediate the fuel and the oxidant so as to prevent mixing of thetwo. In the illustrated embodiment, two working electrodes are provided,each of which is in contact with a different one of the fuel and theoxidant at any given time, so as to drive current to the load in analternating current fashion. For example, when the fuel is in contactwith the working electrode, electrons are driven from that workingelectrode, through the load, and to the working electrode in contactwith the oxidant. When the oxidant and the fuel are switched, the flowof electrons changes directions, but a current still flows through theload.

By allowing the capacitor to remain stationary, the fuel, oxidant, andoptional inert gas can be passed over the working electrodes in a pulsedmanner, as delivered by gases or liquids plumbed to deliver thecompounds in a segregated and regimented manner. For example, theexperimental setup of FIG. 9 could be used to provide such oscillatingcomposition of fuel and oxidant. By quickly oscillating the compositionabove the working electrodes, a particular frequency of alternatingcurrent can be achieved. For example, if the oxidant and fuel aredelivered such that the composition above the working electrodes of twodevices changes 60 times per second, the resulting current will have a60 Hz oscillating alternating current.

The pulsed gas system described with reference to FIGS. 9 and 11 can beextended to large scale systems, such as that illustrated in FIG. 12.FIG. 12 illustrates an exemplary system for generating power using“packed bed” configurations of capacitors connected to fuel and oxidantdelivery systems. In the exemplary embodiment illustrated in FIG. 12,oxygen and hydrogen are provided as the oxidant and the fuel,respectively, in gas form, which are controllably connected to two“packed beds” filled with a plurality of capacitors in a high-densityconfiguration. For example, each of the boxes in FIG. 12 may contain 100or more capacitors. The capacitors are electrically connected to acommon load and the two packed beds are each connected to the commonload in such a way that a current flows through the load because one ofthe packed beds is exposed to oxygen while the other is exposed tohydrogen. The fuel and oxidant are then switched, such that the gasflowing through the beds is switched and, therefore, an alternatingcurrent is generated. It will be appreciated that an inert gas can alsobe used to purge the packed beds in between the fuel and oxidant. Theexemplary system illustrated in FIG. 12 would be particularly useful forgenerating large amounts of power, due to the potential for high devicedensity. The power generated would likely not be at typical ACfrequencies, and so the output may be switched such that the load sees adirect current instead of an alternating current. However, it will beappreciated that those of skill in the art could manipulate such highdensity systems to provide any alternating or direct current desired.

In one embodiment, the steps of exposing the working electrode to thefuel and the oxidant comprise flowing the oxidant and the fuel over theworking electrode, separately.

In one embodiment, a purge step is performed intermediate the flowing ofthe fuel and the oxidant over the working electrode, wherein the purgestep comprises flowing a gas or liquid over the working electrode thatdoes not react with the working electrode.

Moving-Device Systems

Rotating devices have been described previously with regard to FIG. 7.Additional details and device designs will now be discussed.

Any conceivable means for exposing the working electrode to alternatingfuel and oxidant environments can be used. While rotating and conveyorsystems are disclosed specifically, the invention is not limited to suchembodiments.

In one embodiment, the capacitor is configured to move alternatinglythrough a fuel region and an oxidant region, with the fuel and oxidantregions separated by a barrier to prevent mixing of the fuel and oxidantgases or liquids.

In one embodiment, the method further comprises an exhaust regionintermediate and sealed from the fuel and oxidant regions as the workingelectrode is moved between regions.

In one embodiment, multiple capacitors are mounted on a solid surfaceand moved between the regions, wherein the multiple capacitors can beelectrically connected independently, electrically connected together inseries or parallel, electrically connected in any combination of these,or electrically connected differently as a function of time.

In certain embodiments, a rotating support can be used to move theworking electrode between the fuel and the oxidant.

In one embodiment, the capacitor is configured to rotate in a rotationplane, wherein the rotation plane comprises the fuel region, configuredto expose the working electrode to the fuel, and the oxidant region,configured to expose the working electrode to the oxidant; and whereinthe method further comprises a step of rotating the capacitor betweenthe fuel region and the oxidant region to perform the steps of exposingthe working electrode to the fuel and the oxidant, respectively.

In one embodiment, the method further comprises an exhaust regionintermediate, and sealed from, the fuel region and the oxidant region inthe rotation plane, wherein the step of generating electrical power isperformed when the working electrode is in the exhaust region.

In one embodiment, multiple capacitors are mounted on a rotation planeand rotated between the regions, wherein the multiple capacitors can beelectrically connected independently, electrically connected together inseries or parallel, electrically connected in any combination of these,or electrically connected differently as a function of time.

Multiple working electrodes can be moved between the fuel and oxidantregions.

In one embodiment, the step of moving the plurality of capacitorscomprises moving the capacitors such that a first capacitor is in thefuel region while a second capacitor is in the oxidant region.

In one embodiment, the plurality of capacitors are all mounted on thesame side of the substrate.

In one embodiment, at least one of the plurality of capacitors ismounted on an opposite side of the substrate.

FIGS. 13A and 13B illustrate an exemplary rotating device system thatincludes two rotated catalytic electrodes with stationary gas phases.Specifically, two working electrodes are exposed to a top surface of arotating disk. The rotating disk rotates between a fuel region and anoxidant region such that it is possible for an entire first workingelectrode to be in the fuel region while an entire second workingelectrode is in the oxidant region. By rotating the disk, the workingelectrode is exposed to the fuel and oxidant in an oscillating manner,as required by the methods provided herein. The working electrodes andcounter electrodes are connected as necessary to charge and dischargethe capacitor to produce electrical power. It will be appreciated thatmany different design schemes can be used in such a rotating diskmethod. As illustrated in the second sketch in FIG. 13, the workingelectrodes can take any number of shapes, and any number of workingelectrodes can be disposed on the rotating disk. That is, the devicesare not limited such that only one working electrode can be in one ofthe fuel or oxidant regions at one time.

By including multiple working electrodes, one of skill in the art willappreciate that the devices can be connected in such a way as toincrease the frequency of the pulses (e.g., the AC power generated)because the paired working electrodes will be producing alternatingcurrent at a rate equal to the speed of rotation of the disk times thenumber of pairs of working electrodes.

In one embodiment, the plurality of capacitors are in electroniccommunication such that the working electrodes are connected to oppositeterminals of the same electric load.

In one embodiment, the plurality of capacitors are electricallyconnected to provide a desired voltage, current, pulsed voltage, pulsedcurrent, or alternating current frequency.

In one embodiment, the plurality of capacitors have working electrodesdisposed within a plurality of fuel chambers, oxidant chambers, andexhaust chambers.

It will be appreciated that the rotating disk devices as illustratedherein can include three or more separate chambers containing fuel,oxidant, and optional chambers providing inert gases or exhaust ports.FIG. 14A illustrates a three-chamber rotating disk device wherein a fuelchamber, an oxidant chamber, and an exhaust chamber are all disposedseparately above the rotating disk. In the illustrated exemplaryembodiment wherein the fuel is hydrogen, the oxidant is oxygen, and theproduct of the method is water, the exhaust chamber is listed as an H₂Oexhaust. However, it will be appreciated that when the composition ofthe fuel and/or oxidant is different, the exhaust chamber will beconfigured to exhaust (dispose of) whatever the reaction productremaining on the working electrode after a power generation cycle is.FIG. 14B illustrates a modified version of the device of FIG. 14A,wherein the oxidant chamber is larger than the fuel and exhaustchambers. Such a modification illustrates a possible design modificationthat can be used to control pressure, concentration, etc., as well as toillustrate that an equally proportionate chamber division (e.g., FIG.14A) is not necessary.

Double-sided devices can also be used with rotating disk, or otherdevice configurations. In FIGS. 16A and 16B, double-sided devices areillustrated, wherein a mechanical support is used to support capacitorsmounted to both a top and a bottom side of the support. The top andbottom sides of the support are exposed to the fuel and oxidant asnecessary to drive the flow of current through a load. By using adouble-sided rotating disk, the capacity of the device is essentiallydoubled. The support can be the CE (e.g., FIG. 16A) or can be separatefrom the CE (e.g., FIG. 16B).

Conveyor Belt Systems

In addition to the rotating disk devices described herein, other meansfor mechanically moving the capacitor between fuel and oxidant regionsare also provided. For example, FIGS. 15A and 15B illustrate a “conveyorbelt” style device whereby a plurality of capacitors are mounted on abelt that mechanically moves the capacitors between a fuel region and anoxidant region (hydrogen and air, respectively). By connecting thecapacitors properly, electrons flow through a load to generate acurrent. As illustrated in FIG. 15B, a double layer belt is alsocontemplated so as to double the capacity of the device.

In one embodiment, the capacitor is mounted to a conveyor belt thatmoves the working electrode between the fuel region and the oxidantregion.

In one embodiment, the method further includes an exhaust regionintermediate, and sealed from, the fuel region and the oxidant regionalong the path of the conveyor belt, wherein the step of generatingelectrical power is performed when the working electrode is in theexhaust region.

In one embodiment, multiple capacitors are mounted on a conveyor beltand moved between the regions, wherein the multiple capacitors can beelectrically connected independently, electrically connected together inseries or parallel, electrically connected in any combination of these,or electrically connected differently as a function of time.

Enhanced Surface Area Devices

FIGS. 17A and 17B illustrate an exemplary device configuration having anenhanced area working electrode. FIG. 17A is a top plan view. FIG. 17Bis a cross-sectional view. While square posts projecting from thesurface of the device are illustrated, it will be appreciated that anyother shape is contemplated, such as cylinders and otherthree-dimensional polygons. It will also be appreciated that theprojections need not extend exactly perpendicular to the surface of thedevice, as illustrated, but traditional fabrication methods (e.g.,lithography and thin film depositions) make such perpendicularprojections preferable. It will be noted in the cross-sectional view inFIG. 17B that the counter electrode forms the core of the post, and thedielectric and working electrode are conformally coated on the post suchthat the thickness of the dielectric and the working electrode areconsistent regardless of whether on the horizontal or vertical surfacesof the device (to the extent possible based on the fabrication methods).

In one embodiment, the capacitor has a high surface area configurationcomprising a plurality of pillars or ridges projecting from the workingelectrode surface of the capacitor.

In a further embodiment, the plurality of pillars or ridges each has acore comprising the counter electrode, the dielectric coating thecounter electrode, and the working electrode coating the dielectric.

In one embodiment, the capacitor is comprised of a plurality ofnanowires that act as the counter electrode, wherein each nanowire iscoated with the dielectric layer and the dielectric layer is coated withthe working electrode layer to form a core/shell/shell wire structure(e.g, Ag metal nanowire core counter electrode/ZrO2 dielectric shell/Ptnanoparticle working electrode or n+-Si nanowire core counterelectrode/SiO2 dielectric shell/Pt impregnated carbon nanoparticle layerworking electrode).

Device Variations

Referring to FIGS. 18A and 18B, scheme are illustrated for a rotatingdisk device whereby multiple working electrodes are used (FIG. 18A) andmultiple gas chamber are used (FIG. 18B) to increase the frequency ofthe power generated by the devices. Referring to FIG. 18A, brushcontacts are provided just prior to the interface between the fuel andoxidant chambers, so as to allow time between introduction of a workingelectrode into either of the fuel or oxidant, and discharge of thatworking electrode. By providing this time (an “induction” time), aperiod of time is allowed for fuel adsorption and disassociation betweenthe ionization and discharge occurs.

In FIG. 18B, increased frequency power can be achieved at the samerotation speed of the disk by providing multiple fuel and oxidantchambers, and configuring the working electrodes accordingly. Forexample, the illustrated device in FIG. 13A would have double the powerfrequency compared to a device having a single fuel and oxidant chamber.

Referring to FIG. 19A, a cylindrical electrode design is providedwherein capacitors are mounted on a cylinder spinning between a fuelregion and an oxidant region. In the exemplary embodiment of FIG. 19A,hydrogen and air (oxygen) are the fuel and oxidant, respectively. Aplurality of capacitors are mounted on a cylinder, which is spun betweenthe oxidant and fuel regions, which are sealed so as to keep separate.FIG. 19B provides a detail of the MIMs mounted on the cylinder.

Referring to FIG. 20, a “triangular shaft” design is provided, whereby atriangular shaft has capacitors mounted on all three surfaces of thetriangular shaft. The points of the triangle are sealingly fittedagainst the interior wall of a circular chamber that is configured toaccept fuel and oxidant, and discharge exhaust as the capacitors turnthrough a full turn so as to produce electrical power in accordance withthe methods described herein. The triangular shaft design of FIG. 20 isessentially a variation on the three-chamber rotating disk designillustrated in FIG. 14. However, it will be appreciated that certainscenarios may favor the potential for a long and narrow power generationsystem, such as the triangular shaft would offer, compared to a flat andwide system, as the disk system of FIG. 14A would provide.

In a variation of the triangular shaft design illustrated in FIG. 20, a“Wankel” shaft design can optionally be employed. Referring to FIG. 21,a Wankel shaft system is illustrated whereby a non-symmetric,three-surface shaft is used to control intake, compression, and exhaustin a rotating shaft system. Similar to a Wankel engine, by using anoblate rotor onto which capacitors are mounted, the compressioncharacteristics of the gases introduced into the chamber can becontrolled. Compression can be used to enhance the adsorption of thefuel and/or oxidant. Similarly, vacuum created by the system can be usedto help discharge the reaction product (e.g., water).

As the above-described devices illustrate, there are an almost limitlessnumber of ways which one could employ to rotate a capacitor through afuel region and an oxidant region so as to generate electrical power inaccordance with the methods provided herein. It will be appreciated thatany such device is consistent with the scope of the invention, and theinvention is not limited to the embodiments provided herein.

While illustrative embodiments have been illustrated and described, itwill be appreciated that various changes can be made therein withoutdeparting from the spirit and scope of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
 1. A system configured to generate electricity from a fuel and an oxidant, the system comprising: a first capacitor, comprising: a first working electrode, wherein the first working electrode comprises a catalyst for the electrochemical reaction between the fuel and the oxidant and wherein the first working electrode is configured to adsorb the fuel or the oxidant; a first counter electrode; and a first dielectric configured to physically and electrically separate the first working electrode and the first counter electrode; wherein the system is configured to provide a first switchable electrical connection to the first working electrode and the first counter electrode, the first switchable electrical connection being configured to switch between a first electrical load circuit, a first polarization circuit, and no electrical connection.
 2. The system of claim 1, wherein the first polarization circuit provides electrical communication between the first working electrode and the first counter electrode without additional applied bias.
 3. The system of claim 1, wherein the first polarization circuit comprises a voltage source configured to positively bias the first working electrode and negatively bias the first counter electrode.
 4. The system of claim 1, wherein the first working electrode catalyst is selected from the group consisting of Pt, Pd, all noble metals, Ni, Co, Cu, all transition metals, alloys of the preceding, oxides, supported catalysts, and combinations thereof.
 5. The system of claim 1, wherein the first counter electrode is selected from the group consisting of Al, Cu, Ni, Zn, steel, stainless steel, Pt, any metal, transparent conductors, conducting polymers, carbon materials, doped silicon, any doped or heavily doped semiconductor, nanowires or nanoparticles of the preceding, and combinations thereof.
 6. The system of claim 1, wherein the fuel is a neutral or ionic form of one or more of the following: hydrogen; CO; N₂; NO; NO₂; sulfur; SO₂; syngas; hydrogen sulfide; hydrogen peroxide; lower alkanes; all alkanes, including linear, branched, and cyclic species; all alkenes; all alkynes; all arenes; lower alkane alcohols; partially oxidized, hydroxylated, or sulfonated alkanes, alkenes, alkynes, and arenes; gasoline, kerosene, diesel, JP12, and crude oil; biofuels; ammonia, hydrazine, and methyl amine; boranes; acids; halogens; solvated metal cations; solvated metals and metal containing compounds; particulate metals and metal containing compounds; nanoparticles of any of the preceding; any chemical species that can be electrochemically oxidized; mixtures of any of the preceding; dilutions of the preceding with a solvent or gas; and humidified versions of any of the preceding.
 7. The system of claim 1, wherein the oxidant is air or a neutral or ionic form of one or more of the following: oxygen, ozone, hydrogen peroxides, all peroxides, fluorine, chlorine, bromine, iodine, inorganic acids, organic acids, hypochlorite, chlorate, water, solvated metal cations, solvated metals and metal containing compounds, particulate metals and metal containing compounds, nanoparticles of any of the preceding, any chemical species that can be reduced, mixtures of any of the preceding, dilutions of the preceding with a solvent or gas, and humidified versions of any of the preceding.
 8. The system of claim 1, further comprising: a fuel gas source configured to impinge gaseous fuel on the first working electrode; and an oxidant gas source configured to impinge gaseous oxidant on the first working electrode.
 9. The system of claim 8, wherein the fuel gas source and the oxidant gas source are configured to provide alternating flow of the fuel and the oxidant to the first working electrode.
 10. The system of claim 8, wherein the fuel gas source is configured to impinge the fuel on the first working electrode in a first fuel chamber, wherein the oxidant gas source is configured to impinge the oxidant on the first working electrode in a first oxidant chamber, and wherein the system is configured to move the working electrode between the first fuel chamber and the first oxidant chamber.
 11. The system of claim 10, wherein the system is configured to move the working electrode between the first fuel chamber and the first oxidant chamber by a mechanism selected from the group consisting of rotational motion and linear motion.
 12. The system of claim 1, further comprising a second capacitor, comprising: a second working electrode, wherein the second working electrode comprises a catalyst for the electrochemical reaction between the fuel and the oxidant and wherein the second working electrode is configured to adsorb the fuel or the oxidant; a second counter electrode; and a second dielectric configured to physically and electrically separate the second working electrode and the second counter electrode; wherein the system is configured to provide a second switchable electrical connection to the second working electrode and the second counter electrode, the second switchable electrical connection being configured to switch between a second electrical load circuit, a second polarization circuit, and no electrical connection; and wherein the first capacitor and the second capacitor are electrically connected in series, electrically connected in parallel, or have no shared electrical connection.
 13. The system of claim 12, wherein the composition of the first capacitor and the second capacitor are the same composition.
 14. The system of claim 12, further comprising a substrate upon which the first capacitor and the second capacitor are disposed.
 15. The system of claim 12, wherein the first dielectric and the second dielectric are a unitary dielectric that physically spans between the first capacitor and the second capacitor.
 16. The system of claim 12, wherein the first electrical load circuit and the second electrical load circuit provide current to a unified electrical load.
 17. The system of claim 16, further comprising a plurality of additional capacitors configured to provide current to the unified electrical load.
 18. The system of claim 17, wherein the first capacitor, the second capacitor, and the plurality of additional capacitors are arranged in a packed bed configured to receive the fuel and the oxidant sequentially.
 19. The system of claim 12, wherein the first electrical load circuit and the second electrical load circuit provide current to different electrical loads.
 20. A system configured to generate electricity from a fuel and an oxidant, the system comprising: a capacitor, comprising: a working electrode, wherein the working electrode comprises a catalyst for the electrochemical reaction between the fuel and the oxidant and wherein the working electrode is configured to adsorb the fuel or the oxidant; a counter electrode; and a dielectric that physically and electrically separates the working electrode and the counter electrode; means for exposing the working electrode to the fuel; means for charging the capacitor by biasing the working electrode such that it becomes positively charged and biasing a counter electrode of the capacitor such that it becomes negatively charged; and means for the exposing the working electrode to the oxidant; wherein the system is configured to provide a switchable electrical connection to the working electrode and the counter electrode, the switchable electrical connection being configured to switch between an electrical load circuit, a polarization circuit, and no electrical connection. 